IMATRA, Finland (AP) — The construction of barbed-wired fence along Finland’s long border with Russia – primarily meant to curb illegal migration – has broken ground near the southeastern town of Imatra less than two weeks after the Nordic country joined NATO as the 31st member of the military alliance.

The Finnish Border Guard on Friday showcased the building of the initial three kilometer (1.8 mile) stretch of the fence to be erected in Pelkola near a crossing point off Imatra, a quiet lakeside town of some 25,000 people.

Finland’s 1,340 kilometer (832 mile) border with Russia is the longest of any European Union member.

Construction of the border fence is an initiative by the border guard that was approved by Prime Minister Sanna Marin’s government amid wide political support last year. The main purpose of the three-meter (10-foot) high steel fence with a barbed-wire extension on top is to prevent illegal immigration from Russia and give reaction time to authorities, Finnish border officials say.

In 2015-2016, Moscow attempted to influence Finland by organising large numbers of asylum-seekers to northern Finnish crossing points in the Arctic Lapland region. Russian authorities were seen deliberately ushering thousands of asylum-seekers – mostly from Iraq, Afghanistan and other Middle East nations – to those border crossing points.

The move was seen as a show of muscle by Moscow. The issue was settled when Finnish President Sauli Niinistö held talks with Russian President Vladimir Putin. The flow of migrants stopped shortly thereafter.

This is a scenario that Finland – a nation 5.5 million people that officially became a NATO member on April 4 – wants to prevent from repeating itself.

Border officials are quick to acknowledge, however, that it was Russia’s invasion of Ukraine on February 24 last year – the main reason for Finland’s quick push to join NATO after decades of military nonalignment – that prompted construction of the border fence.

“Border barrier fence was no kind of political topic before the war (in Ukraine). And actually, it wasn’t a kind of plan of the Finnish border guard,” Brig. Gen. Jari Tolppanen, head of the technical division at the Finnish Border Guard, told The Associated Press. “All changed after the attack (of Russia against Ukraine).”

The pilot section of the fence is scheduled to be completed by this summer, while the barrier will eventually be extended to a maximum of 200 kilometers (124 miles). It will cover areas – in bits and pieces of separate length – mainly in southeastern Finland near the main border crossing points with Russia but it will also have sections up in the Arctic north in Lapland.